Aubrey Jaffer, mostly to support his portable Scheme library SLIB, implemented a provide/require mechanism for many Scheme implementations. Library files in SLIB provide a feature, and when user programs require that feature, the library file is loaded in.
For example, the file random.scm in the SLIB package contains the line
(provide 'random)
so to use its procedures, a user would type
(require 'random)
and they would magically become available, but still have the same names! So this method is nice, but not as good as a full-featured module system.
When SLIB is used with Guile, provide and require can be used to access its facilities.